1. Field of the Invention
The present invention relates to an eye fundus photographing system for photographing a fundus of an eye to be examined, and more particularly to a fluorescent photographing technique for suitably diagnosing a vascular lesion of a retina or a choroid.
2. Description of the Related Art
Eye fundus examination undertakes an important role in an ophthalmologic field and has been conducted mainly using a slit lamp microscope (slit lamp) or a fundus camera. The eye fundus examination using the slit lamp is performed through a front lens located immediately before an eye to be examined to cancel refracting power of a crystalline lens or the like. For the eye fundus examination using the fundus camera, fluorescent photographing for photographing a state of an eye fundus blood vessel in detail has been widely used in addition to normal photographing methods such as monochrome photographing and color photographing.
In the fluorescent photographing of the eye fundus using the fundus camera, a person to be examined is subjected to intravenous injection with a fluorescent dye material (fluorescent agent) and fluorescence radiated from a fluorescent dye material is photographed. Visible fluorescent photographing in a visible light wavelength region or infrared fluorescent photographing in an infrared light wavelength region has been conducted according to a wavelength region of the radiated fluorescence. Generally, fluorescein (FAG) is used as the fluorescent dye material for the visible fluorescent photographing. In addition, indocyanine green (ICG) pigment is used for the infrared fluorescent photographing. In the infrared fluorescent photographing, each of excitation light resulting from the ICG and fluorescence is near-infrared light, so it is suitable to detect a lesion under preretinal hemorrhages or subretinal hemorrhages, detect a lesion of a choroid coat, or understand a state of a new blood vessel. Therefore, the infrared fluorescent photographing has been widely used.
According to JP 2000-316812 A (claim 1 and paragraph [0014]), an example of a fundus camera capable of performing the infrared fluorescent photographing has been disclosed. In order to reduce a cost while illumination efficiency is maintained, the fundus camera described in this document includes an infrared laser and a xenon lamp which serve as fluorescent photographing light sources for the fundus of an eye to be examined. In the early phase of fluorescence, the fundus of the eye to be examined is illuminated with mainly light from the infrared laser to perform moving picture photographing. In the late phase of the fluorescence, the fundus of the eye to be examined is illuminated with mainly light from the xenon lamp to perform still image photographing. The fundus camera described in this document can perform color photographing, visible fluorescent photographing, and infrared fluorescent photographing by switching among photographing modes.
A fundus camera capable of photographing a three-dimensional image of the eye fundus has been proposed. For example, according to an eye fundus image described in JP 05-015499A (paragraphs [0016] to [0018] and FIG. 2), eye fundus reflection light passing through an objective lens is divided into right and left light beams. Those light beams are imaged on a film by separate optical systems to produce a three-dimensional-image.
A parallel shift method is used as a general method of producing a three-dimensional image in the fundus camera. According to this method, a photographing region of the eye fundus is minutely shifted in parallel to obtain two images. The obtained images are synthesized with each other to produce the three-dimensional image. However, in the parallel shift method, the two images used to produce the three-dimensional image are not obtained by simultaneous photographing. Therefore, even when a photographing interval minimizes, it is impossible to obtain an accurate three-dimensional image.
According to JP 09-276227 A (claim 1), an example of a slit lamp used for an eye fundus examination has been disclosed. The slit lamp described in this document includes a main body, a pillar having a chin rest portion for supporting a chin of a person to be examined, an arm pivotably attached to the pillar, a fixation unit pivotably provided substantially in the end portion of the arm, and a lens holder that holds a front lens for observing the eye fundus of the person to be examined. The lens holder is detachably provided in the pivot center of the fixation unit.
A recent establishment of an infrared fluorescent photographing method improves pathologic resolutions of vascular lesions of a retina and a choroid coat. When the pathology is to be understood in more detail, it may be necessary to apply a new photographing mode which cannot be performed by a conventional fundus camera or a conventional slit lamp. For example, if a three-dimensional moving picture image of the eye fundus can be obtained by the infrared fluorescent photographing to observe the three-dimensional moving picture image in real time, a state of a blood vessel may be recognized in extreme detail.